Motor for washing machine

ABSTRACT

A motor for a drum type washing machine is disclosed, wherein noise is reduced. To this end, the drum type washing machine is provided with a washing motor ( 20 ) comprising a stator ( 30 ) fitted at a rear surface of a tub ( 3 ) and having a plurality of slots ( 33 ) on which a coil ( 33   a ) is wound; a rotor ( 40 ) provided at an outer side of the stator ( 30 ) with a permanent magnet ( 41 ) and connected to a washing drum ( 9 ) inside the tub ( 3 ) by a driving shaft ( 17 ); and isolating means ( 50, 60, 70, 80 ) for isolating a gap ( 21 ) between the stator ( 30 ) and the rotor ( 40 ) not to be communicated with the stator ( 30 ) and the rotor ( 40 ).

TECHNICAL FIELD

[0001] The present invention relates to a drum type washing machine, and more particularly, to a brushless DC motor for driving a drum type washing machine.

BACKGROUND ART

[0002] Generally, the drum type washing method performs the washing using a frictional force between the laundry and the drum rotated by driving force of a motor in a state where detergent, washing water and laundry are accommodated in the drum. The aforementioned drum type washing method has some advantages of no-damaging the laundry, preventing tangle of the laundry, and providing an effect of beating and rubbing the laundry.

[0003] One example of such a direct-coupled drum type washing machine will now be described in brief with reference to FIGS. 1 to 4.

[0004]FIG. 1 is a cross sectional view for illustrating the structure of a conventional drum type washing machine, and FIG. 2 is an enlarged view of the circle ‘A’ in FIG. 1.

[0005] As shown in FIGS. 1 and 2, a tub 3 capable of storing washing water is installed in the interior of a cabinet 5, and is provided therein with a drum 9 for accommodating the laundry. The drum 9 is provided at a rear portion thereof with a drum shaft 17 for transferring driving force of a motor 20 to the drum 9.

[0006] A slot 11 is mounted on a front and rear end of the drum shaft 17, respectively, and the tub 3 is provided at a center portion of a rear wall thereof with a slot housing 15 for supporting the slot 11. A supporting bracket 16 is fixed to the rear wall of the tub 3, and a stator 30 which is a part of a direct-coupled motor is fastened to the supporting bracket 16 by means of a plurality of bolts 19.

[0007] The stator 30 includes, as shown in FIG. 3, a ring-shaped frame 31, and a slot 33 provided at an outside of the frame 31 and having a coil 33 a wound around the slot. A coupling rib portion 32 is formed integrally with the frame 31 and inwardly protruded from the frame 31, and has a coupling hole 32 a for fixing the stator 30 to the rear wall of the tub 3.

[0008] Besides the stator 30, the motor 20 includes a rotor 40 shown in FIG. 4, and the rotor 40 is coupled to the rear end of the drum shaft 17 by means of a fixing bolt 18. The drum 9 is directly coupled to the rotor 40, thereby being rotated together with the rotor 40.

[0009] The cabinet 5 is provided at a front side thereof with a door 1, and a gasket 2 is installed between the door 1 and the tub 3. A hanging spring 4 for supporting the tub 3 is provided between an inside of the upper surface of the cabinet 5 and an upper side of the circumference of the tub 3, while a friction damper 10 for attenuating vibration generated from the tub 3 during the spin cycle is provided between an inside of the lower surface of the cabinet 5 and a lower side of the circumference of the tub 3.

[0010] According to the conventional direct-coupled drum type washing machine constructed as described above, the rotor 40 is rotated by the interaction of an electromagnet formed by supplying a power to the stator 30 and a permanent magnet 41 attached to the inside of the rotor 40, and the force transferred to the drum shaft 17 allows the drum 9 to rotate, thereby performing washing and drying.

[0011] However, the conventional direct-coupled drum type washing machine has a problem in that noise is produced due to air friction between the rotor 40 and the stator 30.

[0012] Specifically, if the rotor 40 is rotated at a high speed, rapid air flow happens through a clearance 21 between the stator 30 and the rotor 40, while the air between the stator 30 and the slot 33 remains stationary. Therefore, there is generated a pressure difference between both airs, so that the air between the slots 33 is introduced into the clearance 21 and thus collides with the air flowing through the clearance 21 to generate an explosive sound. At that time, if a frequency of the explosive sound is identical with a natural frequency of the rotor 40 or the stator 30, a resonant sound is generated, so that abhorring sound is amplified. In particular, upon drying, the rotating speed of the rotor 40 becomes more rapid, so that more rapid air flow is formed through the clearance 21 to generate more dominant explosive sound and resonant sound.

[0013] In addition, upon driving the motor 20, since the polarity of each slot 33 is changed at a very high speed, the slot 33 itself vibrates and thus resonance is generated to amplify the noise.

DISCLOSURE OF THE INVENTION

[0014] Accordingly, the present invention is directed to a brushless motor for use in a drum type washing machine that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.

[0015] An object of the present invention is to provide a brushless motor, for use in a drum type washing machine, capable of suppressing noise generated during the operation of the motor.

[0016] Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings.

[0017] To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, there is provided a motor for use in a washing machine, the motor comprising: a stator fixed to a rear surface of a tub, and having a plurality of slots wound with a coil; a rotor provided at an outside of the stator together with a permanent magnet, and directly coupled to a washing drum installed inside the tub by a driving shaft; and isolating means for isolating a clearance between the stator and the rotor such that the stator and the rotor do not communicate with each other.

[0018] The isolating means includes a shield plate for shielding a space formed between the slots.

[0019] Preferably, the shield plate is a unitary piece enclosing all surfaces of the slots facing the permanent magnet to fully close the space between the slots, or is a plurality of unit pieces, each attached to the surface of the adjacent slot facing the permanent magnet to separately close the space between the slots.

[0020] Preferably, the shield plate is made of non-magnetic material, and is made of a non-adhesive film or an adhesive tape. The film or tape is made of heat-shrink resin material.

[0021] Preferably, the isolating means further includes an auxiliary shield plate for closing the space between the permanent magnets.

[0022] The auxiliary shield plate is a unitary piece fully enclosing a surface of the permanent magnet facing the slot to entirely close the space between the permanent magnet, or is a plurality of unit pieces each attached to a surface of the adjacent permanent magnet facing the slot to separately close the space between the permanent magnets.

[0023] On the other hand, the isolating means includes a plug member for filling a space between the slots, and the auxiliary shield plate is made of non-magnetic material.

[0024] The plug member is a unitary piece filling the space between the slot at once, and preferably includes: a hub seated on an upper surface of a frame of the stator; a coupling rib formed at the hub corresponding to the coupling rib for fixing the stator to the tub; and a plurality of tips formed at the hub at a regular interval, each of which is inserted into the space between the slots. The plug member further includes a plurality of reinforcing ribs formed at the hub for reinforcing strength thereof.

[0025] The plug member is a plurality of unit pieces, each separately filling the space between the slots, and preferably, is a plurality of tips, each inserted into the space between the slots.

[0026] According to the plug member of unitary or separate member, the tip is adapted to fill the entire spaces formed between the slots, and a longitudinal section of the tip has an approximately rectangular shape. The tip is adapted to partially fill the space formed between the slots. A longitudinal section of the tip has an approximately triangular shape.

[0027] Preferably, the tip has a hollow portion or recessed groove extended from an upper surface or a lower surface thereof.

[0028] The isolating means further includes an auxiliary plug member filling the space between the permanent magnets.

[0029] The auxiliary plug member is a unitary piece filling the space between the permanent magnet at one, or is a plurality of unit pieces closing separately the space between the permanent magnet.

[0030] According to the present invention, the clearance between the stator and the rotor is isolated from the space between the stator and the rotor, so that it prevents the collision of the air of different flowing speed to reduce the noise.

[0031] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

[0033] In the drawings:

[0034]FIG. 1 is a cross sectional view for illustrating the structure of a conventional drum type washing machine;

[0035]FIG. 2 is an enlarged view of the circle ‘A’ in FIG. 1;

[0036]FIG. 3 is a perspective view of a stator in FIGS. 1 and 2;

[0037]FIG. 4 is a perspective view of a rotator in FIGS. 1 and 2;

[0038]FIG. 5 is a partially cross sectional view of a motor according to a first embodiment of the present invention;

[0039]FIG. 6 is a cross sectional view taken along a line I-I in FIG. 5;

[0040]FIG. 7 is a perspective view of a shield plate and a stator installed in a motor according to a first embodiment of the present invention;

[0041]FIG. 8 is a perspective view of a shield plate and a stator installed in a motor according to an alternative embodiment of the present invention;

[0042]FIG. 9 is a perspective view of a shield plate and a rotor installed in a motor according to a first embodiment of the present invention;

[0043]FIG. 10a is a perspective view of a plug member of a motor according to a second embodiment of the present invention;

[0044]FIG. 10b is a rear perspective view of FIG. 10a;

[0045]FIG. 11a is a plan view of FIG. 10b;

[0046]FIG. 11b is a cross sectional view taken along a line II-II in FIG. 11a;

[0047]FIG. 12 is a plan view for illustrating an assembled state of a plug member and a stator according to a second embodiment of the present invention;

[0048]FIG. 13a is a perspective view of an alternative view of a plug member according to a second embodiment of the present invention;

[0049]FIG. 13b is a rear perspective view of FIG. 13a;

[0050]FIG. 14a is a plan view of FIG. 13b;

[0051]FIG. 14b is a cross sectional view taken along a ling III-III in FIG. 14a; and

[0052]FIG. 15 is a perspective view of a plug member and a rotor installed in a motor according to a second embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0053] Reference will now be made in detail to first and second preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In the embodiments, like parts are shown by corresponding reference numerals throughout the drawings, and additive explanation thereof will be omitted.

[0054] First Embodiment

[0055] The first embodiment of the present invention will now be described in detail with reference to FIGS. 5 to 9. FIG. 5 is a partially cross sectional view of a motor according to the first embodiment of the present invention, and FIG. 6 is a cross sectional view taken along a line I-I in FIG. 5. FIG. 7 is a perspective view of a shield plate and a stator installed in the motor according to the first embodiment of the present invention, and FIG. 8 is a perspective view of the shield plate and the stator installed in the motor according to an alternative embodiment of the present invention.

[0056] As shown in drawings, a motor 20 for use in a washing machine according to the first embodiment generally includes a stator 30 fixed to a rear surface of a tub 3, and a rotor 40 provided outside the stator at a predetermined clearance 21. The motor 20 of the present invention further includes an isolating member for isolating the clearance 21 between the stator 30 and the rotor 40.

[0057] The stator 30 is provided with a plurality of slots 33, which are radially disposed, and about which coil 33 a is wound. The rotor 40 has a plurality of permanent magnets 41 enclosing the slots 33, and is directly coupled to a washing drum 9 installed inside the tube 3 by means of a driving shaft 17. Accordingly, the clearance 21 is substantially formed between the slot 33 and a permanent magnet 41. Also, the isolating member isolates the clearance 21, so that the clearance 21 does not communicate with the stator 30 and the rotor 40. In the motor 20 of the present invention, since the stator 30 and the rotor 40 are identical in their structures to those of the conventional motor described previously with reference to FIGS. 1 to 4, the isolating member will now be described in detail.

[0058] The isolating member includes shield plates 50 and 51 for shielding a space 34 between the slots of the stator 30.

[0059] As shown in FIGS. 6 and 7, the shield plate may be a unitary piece fully enclosing the surface of the slots 33 facing the permanent magnet 41. Specifically, the shield plate 50 is continuously extended along a radially outer end surface of the slot 33, so that the shield plate 50 has substantially a ring shape to shield the space 34 between the slots 33 at once.

[0060] As shown in FIG. 8, the shield plate 51 of the stator 30 may consist of a plurality of unit pieces each attached to the surface of the adjacent slot 33 facing the permanent magnet. Specifically, the shield plate 50 is discontinuous along the radially outer end surfaces of the adjacent slots 33. The shield plate 50 closes separately the space 34 between the slots 33, so that the space 34 may be closed by using less material relative to the case of using the shield plate 50 of unitary piece.

[0061] When power is applied to the motor 20, if the shield plates 50 and 51 are magnetized, the operation of the motor may be hindered. In order to prevent the above problem, it is preferable to manufacture the shield plate with nonmagnetic material. In other words, the shield plates 50 and 51 may have any one of a non-adhesive flexible film and an adhesive tape.

[0062] In case of employing the film, the shield plate 50 of unitary piece may be forcibly fitted in the radially outer end surfaces of the slot 33, while the shield plate 51 of unit piece has to be attached by use of separate adhesive. In addition, in case of employing the adhesive tape, the shield plates 50 and 51 may be easily attached to the radially outer end surfaces of the slot 33.

[0063] In these cases, the shield plates 50 and 51 play a role in holding the slot 33 not to be vibrated, as well as a role in closing the space 34. In particular, in case that the film or tape is made of heat-shrink resin material, the shield plates 50 and 51 is shrunk by heat generated from the operation of the motor 20, thereby more firmly holding the slots 33.

[0064] Since there is a space 42 between the permanent magnets 41 of the rotor 40 even through it is minute, the isolating member further includes an auxiliary shield plate 60 for closing the space 42 between the permanent magnets 41, as shown in FIG. 9. The clearance 21 between the stator 30 and the rotor 40 may be completely isolated.

[0065] The auxiliary shield plate 60 may be a plurality of unit pieces, which are attached to the surfaces of two adjacent permanent magnets facing the slot 33, respectively, and separately close the space 42 between the permanent magnets 41, as shown in FIG. 9. Although not shown in the accompanying drawings, the auxiliary shield plate may be a ring-shaped unitary piece fully enclosing the entire surfaces of the permanent magnet 41 facing the slot 33, i.e., substantially enclosing the inner periphery of the permanent magnet 41, to close the spaces 42 at once, like the shield plate 50 mentioned above.

[0066] Preferably, the auxiliary shield plate 60 is made of non-magnetic material to prevent the operation of the motor 20 from being hindered. In this case, the auxiliary shield plate 60 may be either a non-adhesive flexible film or an adhesive tape. More preferably, the film or tape is made of heat-shrink material.

[0067] In the first embodiment, the shield plates 50 and 51 and the auxiliary shield plate 60 have a thin thickness enough to prevent the interference between the rotor 40 and the stator 30, and although it is shown in the drawings that the shield plates 50 and 51 and the auxiliary shield plate 60 are made of transparent material, they may be made of semi-transparent or opaque material.

[0068] The operation of the motor according to the first embodiment of the present invention will now be described.

[0069] If the rotor 40 is rotated at a high speed, rapid air flow is formed through the clearance 21 between the stator 30 and the rotor 40 to lower the pressure therebetween, while since the air in the spaces 34 between the slots 33 remains stationary, the air pressure in the spaces 34 becomes relatively higher compared with that between the clearances.

[0070] During the operation of the motor 20, the shield plates 50 and 51 close the space 34, thereby isolating the clearance 21 from the space 34. Specifically, the shield plates 50 and 51 prevent the communication between the space 34 and the clearance 21. Accordingly, in spite of the pressure difference, the air remaining stationary in the space 34 does not flow into the clearance 21, and thus does not collide with the air flowing rapidly into the clearance 21. As a result, explosive sound or resonant sound due to the collision or friction of the airs in the clearance 21 and the space 34 is prevented. In addition, the space 42 between the permanent magnets 41 is closed by the auxiliary shield plate 60 although it is minute, so that the clearance 21 is completely isolated from the spaces 34 and 42. Accordingly, the occurrence of noise may be remarkably reduced during the operation of the motor.

[0071] Meanwhile, when the motor 20 is driven, the polarity of each of the slots 33 is changed at a high speed, so that the slot 33 that itself vibrates and thus resonance may be generated. The shield plates 50 and 51 of the present invention fix securely the slot 33, thereby preventing noise from being generated due to the vibration of the slot. In addition, the auxiliary plate 60 can prevent the vibration of the permanent magnet 41.

[0072] Second Embodiment

[0073] The second embodiment of the present invention will now be described in detail with reference to FIGS. 10a to 15. FIG. 10a is a perspective view of a plug member of a motor according to the second embodiment of the present invention, FIG. 10b is a rear perspective view of FIG. 10a, FIG. 11a is a plan view of FIG. 10b, and FIG. 11b is a cross sectional view taken along a line II-II in FIG. 11a. FIG. 12 is a plan view for illustrating an assembled state of the plug member and the stator according to the second embodiment of the present invention.

[0074] A motor 20 for use in a washing machine according to the second embodiment generally includes a stator 30 fixed to a rear surface of a tub 3, a rotor 40 provided outside the stator 30 at a predetermined clearance 21, and an isolating member for isolating the clearance 21 between the stator 30 and the rotor 40. Since the stator 30 and rotor 40 are substantially identical in their structures to those of the first embodiment, their detailed description is omitted and accordingly detail description on the isolating member is given below.

[0075] According to the second embodiment of the present invention, the isolating member includes a plug member 70 filling a space 34 between the stator 30 and the slot 33.

[0076] The plug member 70 may be a unitary piece filling the spaces between the respective slots 33 at once, as shown in accompanying drawings. Preferably, the plug member 70 is made of non-magnetic material to prevent an electrical interference with the stator 30. Specifically, as shown in FIG. 10a, the plug member 70 includes a hub 71 seated on an upper surface of a frame 31 of the stator 30, a coupling rib 72 formed at the hub 71, and a plurality of tips 73 formed at the hub at a regular interval. Preferably, the plug member 70 further includes reinforcing ribs 74 a and 75 b for reinforcing strength thereof as shown in FIG. lob.

[0077] The hub 71 has the same shape as the frame 31. The rib 72 is integrally protruded from an inner periphery of the hub 71 so as to correspond to the coupling rib 32 for fixing the stator 30 to the tub 3, and includes a coupling hole 72 a with a desired size. The reinforcing ribs 74 a and 74 b are substantially formed at a rear surface of the hub 71, and are formed along a radial and circumferential direction, respectively, as apparently shown in FIG. 11a.

[0078] The tips 73 are integrally formed along an outer periphery of the hub 71, and are inserted into each space between the slots 33, respectively. According to the second embodiment of the present invention, the tips 73 may be formed to fully fill the space 34 between the slots 33. In this case, the longitudinal section of the tip 73 has an approximately rectangular shape, as shown in FIG. 11b. Meanwhile, if the tip 73 isolates the space 34 and the clearance 21 from each other, it is not always necessary to fully fill the space 34 between the slots. Accordingly, the tip 73 may be formed to partially fill the space 34 between the slots 33, and thus the longitudinal section of the tip 73 has an approximately triangular shape. Preferably, the radial end of the tip 73 is formed to close at least the space 34 between the slots and to thus isolate the space 34 and the clearance 21. By employing the partial tip 73, the plug member 70 filling the space 34 can be manufactured by less amount of material.

[0079] Further, since the tip 73 may have a hollow portion or a recessed groove 73 a extended from an upper or lower surface as shown in FIGS. 11a and 11 b, it is possible to reduce the amount of the material required to manufacture the plug member 70.

[0080] Furthermore, since the tip 73 having the hollow portion or recessed groove 73 a is slightly elastic, it may be forcibly fitted between the slots 33, so that the tip 73 fixes the slot 33 so as not to vibrate during the operation of the motor.

[0081] A process of assembling the plug member 70 and the stator 30 will now be described.

[0082] The plug member 70 is fixed to the rear wall of the tub 3 together with the stator 30 after the stator 30 and plug member 70 have been assembled. Specifically, in state where the coupling rib 32 of the stator is matched with the coupling rib 72 of the plug member 70, the tip 43 is inserted between the slots 33. As a result, the coupling hole 32 a of the coupling rib 32 is aligned with the coupling hole 72 a of the coupling rib 72, and the coupling member 19 penetrates through the coupling holes 32 a and 72 a to be coupled to the rear wall of the tub 3, so that assembling process of the stator 30 and the plug member 70 is completed.

[0083] Although not shown in the accompanying drawings, the plug member may consist of a plurality of unit pieces separately filling each space 34 between the slots 33. The plug member may be a plurality of tips, each being inserted into the space 34, and the tip may be manufactured in a structure having some modules filling the spaces 34 every certain area in a circumferential direction of the stator 30. Such the plug member provides an effect of reducing material consumption, and each tip has the same characteristic as the tip 73 described with reference to FIGS. 10a to 14 b.

[0084] On the other hand, the isolating member preferably further includes an auxiliary plug member filling the space 42 between the permanent magnets 41 so as to completely isolate the clearance 21 between the stator 30 and the rotor 40. The auxiliary plug member 80 may be a plurality of unit pieces separately closing the spaces 42, as shown in FIG. 15, or may be a unitary piece filling the spaces 42 between the permanent magnets 41 having a similar shape to the plug members 70 at once. Preferably, the auxiliary plug member 80 is made of non-magnetic material.

[0085] The auxiliary plug members commonly include tips inserted into the spaces 42, and it can be understood that these tips have the same characteristic as the aforementioned tip 73. The tip is formed to fully or partially fill the space 42 between the permanent magnets 41. The tip may have a hollow portion or a recessed groove, and is forcibly fitted between the permanent magnets 41.

[0086] The operation of the motor according to the second embodiment of the present invention will now be described.

[0087] If the rotor 40 is rotated at a high speed, rapid air flow is formed through the clearance 21 between the stator 30 and the rotor 40 to lower the pressure therebetween, while since the air in the spaces 34 between the slots 33 remains stationary, the air pressure in the spaces 34 becomes relatively higher compared with that between the clearances.

[0088] During the operation of the motor 20, the plug member 70 fills the space 34, thereby isolating the clearance 21 from the space 34. Here, in case the plug member 70 fills the entire spaces 34, the space 34 substantially disappears, so that it becomes impossible to communicate the space 34 with the clearance 21. Accordingly, the noise generated due to the rapid air flow in the clearance 21 is basically prevented. In addition, in case the space 34 is partially filled with the plug member 70, the tip 73 is formed to close the space 34, so that the space 34 is not communicated with the clearance 21. Accordingly, the air flow from the space 34 to the clearance 21 is prevented, and thus the noise generation due to the air collision is also prevented. The auxiliary plug member 80 fills or closes the space 42 between the permanent magnets 41 to effectively reduce the noise generated during the operation of the motor 20.

[0089] Meanwhile, the plug member 70 and the auxiliary plug member 80 are forcibly fitted between the slot 33 and the permanent magnet 41, thereby holding the slot 33 and the permanent magnet 41 and thus preventing noise such as resonance sound from being generated due to the vibration of the slot 33 and the permanent magnet 41.

[0090] While the present invention has been described and illustrated herein with reference to the preferred embodiments thereof, it will be apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of the appended claims and their equivalents.

INDUSTRIAL APPLICABILITY

[0091] With the drum type washing machine of the present invention, the space between the slot and the permanent magnet is closed or filled by the shield plate/auxiliary shield plate or the plug member/auxiliary plug member to isolate the clearance between the stator and the rotor. Accordingly, the space between the slot and the permanent magnet is not communicated with the clearance, thereby substantially preventing the air flow between the space and the clearance. In addition, the slot and the permanent magnet are fixed by the shield plate/auxiliary shield plate or the plug member/auxiliary plug member so as to prevent the vibration thereof.

[0092] Resultantly, the present invention prevents explosive sound due to the air collision and the resonance sound generated during the operation of the motor, thereby improving the confidence of consumers on the product. 

1. A motor for use in a washing machine, the motor comprising: a stator fixed to a rear surface of a tub, and having a plurality of slots wound with a coil; a rotor provided at an outside of the stator together with a permanent magnet, and directly coupled to a washing drum installed inside the tub by a driving shaft; and isolating means for isolating a clearance between the stator and the rotor such that the stator and the rotor do not communicate with each other.
 2. The motor as claimed in claim 1, wherein the isolating means comprises a shield plate for shielding a space formed between the slots.
 3. The motor as claimed in claim 2, wherein the shield plate is a unitary piece enclosing all surfaces of the slots facing the permanent magnet to fully close the space between the slots.
 4. The motor as claimed in claim 2, wherein the shield plate is a plurality of unit pieces each attached to the surface of the adjacent slot facing the permanent magnet to separately close the space between the slots.
 5. The motor as claimed in claim 2, wherein the shield plate is made of non-magnetic material.
 6. The motor as claimed in claim 5, wherein the shield plate is made of a non-adhesive film.
 7. The motor as claimed in claim 5, wherein the shield plate is made of an adhesive tape.
 8. The motor as claimed in claim 6 or 7, wherein the film or tape is made of heat-shrink resin material.
 9. The motor as claimed in claim 2, wherein the isolating member further comprises an auxiliary shield plate for closing the space between the permanent magnets.
 10. The motor as claimed in claim 9, wherein the auxiliary shield plate is a unitary piece fully enclosing a surface of the permanent magnet facing the slot to entirely close the space between the permanent magnet.
 11. The motor as claimed in claim 9, wherein the auxiliary shield plate is a plurality of unit pieces each attached to a surface of the adjacent permanent magnet facing the slot to separately close the space between the permanent magnets.
 12. The motor as claimed in claim 9, wherein the auxiliary shield plate is made of non-magnetic material.
 13. The motor as claimed in claim 12, wherein the auxiliary shield plate is made of a non-adhesive film.
 14. The motor as claimed in claim 12, wherein the auxiliary shield plate is made of an adhesive tape.
 15. The motor as claimed in claim 13 or 14, wherein the film or tape is made of heat-shrink resin material.
 16. The motor as claimed in claim 1, wherein the isolating means comprises a plug member for filling a space between the slots.
 17. The motor as claimed in claim 16, wherein the plug member is a unitary piece filling the space between the slot at once.
 18. The motor as claimed in claim 17, wherein the plug member comprises: a hub seated on an upper surface of a frame of the stator; a coupling rib formed at the hub corresponding to the coupling rib for fixing the stator to the tub; and a plurality of tips formed at the hub at a regular interval, each of which is inserted into the space between the slots.
 19. The motor as claimed in claim 18, wherein the plug member further comprises a plurality of reinforcing ribs formed at the hub for reinforcing strength thereof.
 20. The motor as claimed in claim 16, wherein the plug member is a plurality of unit pieces, each separately filling the space between the slots.
 21. The motor as claimed in claim 16, wherein the plug member is a plurality of tips each inserted into the space between the slots.
 22. The motor as claimed in claim 18 or 21, wherein the tip is adapted to fill the entire spaces formed between the slots.
 23. The motor as claimed in claim 22, wherein a longitudinal section of the tip has an approximately rectangular shape.
 24. The motor as claimed in claim 18 or 21, wherein the tip is adapted to partially fill the space formed between the slots.
 25. The motor as claimed in claim 24, wherein the tip has an end closing the space between the slots.
 26. The motor as claimed in claim 24, wherein a longitudinal section of the tip has an approximately triangular shape.
 27. The motor as claimed in claim 18 or 21, wherein the tip has a hollow portion or recessed groove extended from an upper surface or a lower surface thereof.
 28. The motor as claimed in claim 18 or 21, wherein the tip is forcibly fitted between the slots.
 29. The motor as claimed in claim 16, wherein the plug member is made of non-magnetic material.
 30. The motor as claimed in claim 6, wherein the isolating member further comprises an auxiliary plug member filling the space between the permanent magnets.
 31. The motor as claimed in claim 30, wherein the auxiliary plug member is a unitary piece filling the space between the permanent magnet at one, or is a plurality of unit pieces closing separately the space between the permanent magnet.
 32. The motor as claimed in claim 31, wherein the auxiliary plug member comprises a plurality of tips each inserted into the space between the permanent magnets.
 33. The motor as claimed in claim 32, wherein the tip is adapted to fill the entire spaces formed between the permanent magnets.
 34. The motor as claimed in claim 33, wherein a longitudinal section of the tip has an approximately rectangular shape.
 35. The motor as claimed in claim 32, wherein the tip is adapted to partially fill the space formed between the permanent magnets.
 36. The motor as claimed in claim 35, wherein the tip has an end closing the space between the permanent magnets.
 37. The motor as claimed in claim 35, wherein a longitudinal section of the tip has an approximately triangular shape.
 38. The motor as claimed in claim 32, wherein the tip has a hollow portion or recessed groove extended from an upper surface or a lower surface thereof.
 39. The motor as claimed in claim 32, wherein the tip is forcibly fitted between the permanent magnets.
 40. The motor as claimed in claim 30, wherein the plug member is made of non-magnetic material. 